Apparatus for handling connectors

ABSTRACT

An array of bent wire connectors to grip the edge of a printed circuit board is held in spaced, opposed grooves on facing side walls of a holder so that the whole array can be affixed to a mother board as a unit by soldering the free ends of the connectors in place. The grooves can be preformed to hold the connectors in the array, or they can be formed in situ by heating a jig with the connectors assembled in a similar array of holes in the surface of the jig and then pressing a thermoplastic holder onto the connectors. The heated connectors soften the contiguous portions of the holder, and after the latter is in place, the assembly is allowed to cool so that the thermoplastic material can reharden in gripping relation to the connectors. A bar can separate gripping portions of the connectors to align them and give them a pre-set position to receive the edge of the printed circuit board easily.

This is a division of application Ser. No. 504,233, filed Sept. 9, 1974now U.S. Pat. No. 3,940,849.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of wire form connectors andparticularly to a system and apparatus for handling the wire formconnectors so that a large number of them may be simultaneously insertedinto one printed circuit structure to grip onto the edge of anotherprinted circuit structure and furnish electrical connection between thetwo printed circuit structures.

2. The Prior Art

This invention relates to the type of electrical connectors described inmy U.S. Pat. No. 3,340,440. These connectors may be described asgenerally U-shaped with a central reverse bend or as being generallyM-shaped. Each connector is a single piece of wire with two outer legsthat extend generally parallel to each other in one direction and arejoind together by a curved bight section. Instead of a single curvedsection, the bight has a reverse bend in it so that the overallconnector takes generally the shape of an M. The reverse-bent centralsection is defined by parts of the wire that extend generally in thesame direction as the outer ends but the spacing between these two partsof the reverse bend is not uniform. It is smaller at the entrance of thereverse bend to form gripping portions, or jaws, capable of gripping theedge of a printed circuit board or the like. The extent of insertion ofthe printed circuit board between the two spaced apart gripping portionsis limited by the length of the reverse-bent portion. The closed end ofthe reverse-bent portion may be relatively circularly curved or it maybe more nearly straight with sharp curves joining the parts that formthe gripping members. In the latter case, there is a more definitelocation of the edge of a printed circuit board or the like insertedbetween the gripping portions.

Such connectors have been inserted into printed circuit boards and thelike by drilling or forming holes in the printed circuit board in theproper position to receive a second printed circuit board. Normally, theholes are formed in pairs to receive each of the free ends of eachconnector and the pairs of holes are arranged in two parallel straightlines since the printed circuit board to be inserted between thegripping portions of the aligned connectors is normally straight.

One of the disadvantages of using such connectors is the necessity ofinserting each of them separately. In some cases they may be inserted bya machine, but often it is just as economical to insert themindividually by hand. The structure into which they are insertedincludes metallized areas around each of the holes so that each of theends of the connectors can be soldered thereto. This is usually done byplacing the entire structure over a soldering vessel and causing a waveof solder to wash across the metallized areas and the ends of theconnectors. It is preferable to provide means to hold the grippingportions in alignment so that they will remain aligned after thesoldering operation has been completed.

It is one of the objects of the present invention to provide a methodand apparatus for handling the connectors in groups so that they neednot all be inserted separately into holes in a printed circuit board orthe like.

It is another object to provide for pre-setting the gripping portions ofthe connectors so that they will apply a certain pressure to a printedcircuit member or the like in use.

It is still another object of the present invention to provide inherentcorrect alignment of a number of such connectors prior to the time theyare inserted into the printed circuit board in which they are to besoldered.

A still further object is to provide an improved holding structure toreceive connectors of the aforementiond type.

Another object is to provide for easy removal of a holder after it hasserved its purpose in facilitating attachment of a group of connectorsto a printed circuit board.

Still further objects will become apparent to those skilled in the artafter studying the following specification and drawings.

SUMMARY OF THE INVENTION

In accordance with this invention a unitary article is formed of aplurality of connectors, which are of a type shown and described in U.S.Pat. No. 3,340,440, and a holder that grips the connectors in apredetermined aligned array. The holder has a pair of side walls thatextend the full length of the array of connectors and at least a shortdistance beyond each end of the array. The free ends of all of theconnectors extend beyond one of the long edges of the side walls so thatthey can be inserted in correspondingly aligned holes in a printedcircuit member, commonly referred to as a mother board, and supported bythe holder while being soldered in place.

The side walls of the holder are joined together by a transversestructure that may be a third wall joining the other long edge to form astructure of U-shaped cross-section or may be a plurality of transversewalls. The inwardly facing surfaces of the side walls have parallelgrooves to hold the connectors in proper alignment and each groove inone side wall is directly opposite a groove in the other side wall sothat the legs of each connector can be held in a pair of opposedgrooves. The holder may be made of any suitable material, such as athermoplastic material molded into the proper shape and having moldedgrooves to receive the connectors or, in the case of a holder having aU-shaped cross-section, extruded.

If the holder is extruded, the grooves, which are perpendicular to thedirection of extrusion, are formed in situ. The method for forming thegrooves with the connectors positioned therein requires that the arrayof connectors first be assembled by having their free ends inserted inproperly aligned pairs of holes in a jig which is either in the form ofa heat-conductive block or in the form of a plurality of heat-conductiveblocks held in rigid, spaced relationship to each other to compensatefor heat expansion of the blocks. The assembly of connectors and jig isthen heated, for example, in an oven, to bring the legs of theconnectors to a high enough temperature to soften the contiguous surfaceareas of the holder as the latter is pressed upon the assembledconnectors in a direction parallel to the legs. The block and connectorsare then allowed to cool enough so that the softened regions of theholder reharden in precisly fitting relationship to grip at least aportion of each leg of each connector.

Prior to placing the holder over the connectors, an alignment bar can beforced into the reverse-bent section of the M-shaped connectors. The barnot only aligns the connectors but spaces the gripping portions acertain distance apart. The rehardened holder side walls will retain thesides of the connectors to keep the gripping portions separated furtherthan they would normally be and thus pre-set the connectors to have acertain gripping force on the edge of a printed circuit board of acertain thickness. After the holder and connectors have been joinedtogether and cooled, the alignment bar is removed, and theholder-and-connector assembly is removed from the jig.

When the connectors are to be inserted in previously formed holes in aprinted circuit board or the like, the holder may be placed in positionto allow the ends of the legs of the connectors to fit into the holes onthe printed circuit board and all of the legs sealed in place preferablyby a wave of molten solder. The holder may be removed immediately afterthe soldering operation due to the fact that the molten solder providesenough heat to loosen the thermoplastic material. Alternatively, theholder may be left in place until the holder has cooled and may later beremoved by applying sufficient heat, for example by radiant lamp or aheat gun or the like, to soften the thermoplastic holder. Only arelatively low degree of heat need be applied to loosen the holder forremoval. The connectors are then fixed in place on the printed circuitboard and are ready to receive between their gripping portions anotherprinted circuit or the like. Because the alignment bar may be chosen tohave an exact thickness, the distance between the gripping portions ofthe connectors may be fixed so that they will receive a printed circuitboard and apply a certain pressure thereto. In this way a relativelylarge number of connectors can be placed so as to receive a singleprinted circuit board and yet the total force exerted by the connectorson the edge of the printed circuit board can be held to an amount thatpermits the board to be relatively easily inserted and removed, contraryto connectors built into a support structure and not available foreasily setting the resilient bias of their gripping portions.

If a larger number of connectors is to be aligned and held by a singleholder, means must be provided so that the spacing between them does notchange as the jig with the array of connectors on it is allowed to cool.If there is excessive contractions of the jig during cooling, the holderwill warp. The use of a material such as Invar, which has a low thermalcoefficient of expansion, for the jig eliminates any problem due toshrinkage, but Invar is expensive and difficult to machine, and asubstitute is desired. One such substitute is to make the jig of aneasily machined material, such as brass and divide the jig into severalrelatively short segments joined together by a rod of a lowercoefficient of expansion, such as steel. The rod and jig segments aregripped at certain points so that expansion in the segments takes placein both directions parallel to the axis of the rod and can thus bedivided relatively equally in the two directions. This minimizes thetotal expansion of the support member, which minimizes the shift inspacing between the connectors as they cool down.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a connector of the type to be handled by themethod and apparatus of the present invention.

FIG. 2 shows the connector of FIG. 1 installed on a printed circuitboard and making connection with a second printed circuit board.

FIG. 3 shows an array of connectors of the type shown in FIG. 1 placedin a support member to be assembled with a holder.

FIG. 4 shows the support member of FIG. 3 with a holder placed over theconnectors.

FIG. 5 is a cross-sectional view of a modified form of support memberwith a large number of connectors mounted on it.

FIG. 6 is a plan view of a modified form of holder.

FIG. 7 is a cross-sectional view of the holder in FIG. 6 along the line7-7'.

FIG. 8 shows a connector in a different cross-sectional location of theholder in FIG. 6 along the line 8-8'.

FIG. 9 shows a holder with connectors in it aligned to place theconnectors in a printed circuit board.

FIG. 10 shows the holder and printed circuit board of FIG. 9 anddiagrammatically illustrates a wave-soldering bath under the printedcircuit board.

FIG. 11 shows the holder of FIG. 10 being removed from the connectorsmounted on the printed circuit board.

FIG. 12 shows a second printed circuit board being inserted into theconnectors on the first printed circuit board.

DETAILED DESCRIPTION OF THE INVENTION

The connector shown in FIG. 1 is a wire member 21 that has twosubstantially parallel legs 22 and 23 joined together at one end andfree at the other end. The end at which they are joined together may bereferred to as the bight end of the connector but instead of being asimple U-shaped bight, it has a reverse-bent, or downwardly bentsection, so that it is more accurately described as M-shaped. Thereverse bent section includes a center portion 24 and two sides 26 and27 joined to the center 24 by relatively sharp bends 28 and 29. Thesides 26 and 27 are joined by smoothly curved sections 31 and 32 to theouter legs 22 and 23, respectively.

As will be noted, the outer legs 22 and 23 are longer than the sides 26and 27, and the sides are closer together at the end where they join thesections 31 and 32, than where they join the center 24. As stated in myU.S. Pat. No. 3,340,440, this structure provides gripping portions 33and 34 that are rounded to press firmly against the opposite sides of aprinted circuit board 36 illustrated in broken lines and shown with anarrow 35 indicating the direction that it is inserted between thegripping portions 33 and 34.

FIG. 2 shows the ends of the legs 22 and 23 inserted through a printedcircuit board 37 and attached by solder connections 38 and 39 tometallized sections 41 and 42, respectively. The printed circuit board37 is defined as a mother board since other boards, such as the board36, are connected to it and supported by it. The board 36 has aconductive section 43 on one surface to be contacted by the grippingportion 34 as the board 36 is gripped between the portions 33 and 34. Aswill be noted, the effect of inserting the board 36, which is somewhatthicker than the normal distance between the gripping portions 33 and34, between the sides 26 and 27 is to force the sides apart slightly inthe directions indicated by the arrows 44 and 46. This causes the legs22 and 23 to be slightly deflected to apply further resilient pressureon the gripping portions 33 and 34 in addition to the pressure providedby the natural resilience that causes the sides 26 and 27 to return tothe position occupied in FIG. 1.

Normally a printed circuit board, such as the mother board 37, wouldhave a large number of aligned connectors 21 to grip individualconductive sections of another board such as the board 36. In accordancewith the present invention, such connectors 21 are shown mounted in ajig in the form of a heat conductive block, or support member, 47 inFIG. 3. The block 47 may be made of any suitable material, such as brassor steel or, preferably, a material that has a low thermal coefficientof expansion, such as Invar. This block has, in the embodiment shown,two rows of holes 48 bored in it and arranged along two straightparallel lines spaced approximately the same distance apart as the legs22 and 23 of the connectors 21. The holes 48 need not extend entirelythrough the block 47, provided they extend far enough to allow thecenter 24 of each of the connectors 21 to rest on the surface of theblock. Furthermore, the holes 48 are slightly oversized and may beslightly countersunk to allow the ends of the legs 22 and 23 of theconnectors 21 to be inserted easily. A U-shaped member 50 that is alittle taller than the connectors may be placed in the array ofconnectors nearer one end of the array than the other to fit into acorresponding slot in the board 36 to keep the board 36 from beinginserted into the array backward.

One of the important advantages of the connectors 21 is that they may beadjusted to provide a desired pressure by the gripping portions 33 and34. In order to do this, it is desirable that a bar 49 be placed in thereverse-bent sections of all of the connectors 21 in the block 47. Asindicated by the arrow 51, the bar 49 is pressed downwardly between theportions 26 and 27 of all of the connectors 21, except it must beinserted before member 50 is in place. The thickness T of the bar ischosen to space the gripping portions 33 and 34 apart by a certaindistance so that, when the connectors 21, which are thus given aninitial resilient bias, are placed in the printed circuit board 37 shownin FIG. 2, they will all not only be aligned with each other to receivethe printed circuit board 36 easily, but will all press upon the printedcircuit board 36 with a certain pressure that is great enough to makegood contact between the gripping portion 34 and the conductive layer 43but is not so great as to make it excessively difficult to push theprinted circuit board 36 into gripping engagement with the connectors 21or to remove it from the connectors. Forcing the bar 49 between thegripping portions 33 and 34 causes the legs 22 and 23 to pivot so thatthey point toward a common location instead of being parallel. Thethicker the bar the greater the deflection of the legs. The actualdeflection is small, and the slightly oversized holes in the printedcircuit board 37 in FIG. 2 allow the legs 22 and 23 to enter at anangle. The solder connections 38 and 39 keep the legs 22 and 23 tiltedat a slight angle, thus retaining a certain spacing between the grippingportions 33 and 34.

After the bar 49 has been placed in position so that it rest within thereverse-bent part of each of the connectors 21 in FIG. 3, the assemblyof the block 47 and connectors 21 and, if used, the block 47 is heated,for example by placing the assembly in an oven.

When the assembly reaches a certain temperature, it is removed from theoven, and a suitable holder 52 shown in FIG. 4 is placed over the heatedconnectors 21 on the block 47. The holder 52 is preferably athermoplastic material that is relatively hard such as, for example, ahard grade of pure vinyl chloride of approximately 90 durometer. Theholder 52 is generally U-shaped and its central channel 53 has sidewalls that press against the outer legs 22 and 23 of each of theconnectors 21 and of the member 50, which is not so tall that it willnot fit in the channel 53. The temperature of the heated connectors 21and member 50 is hot enough to cause the contiguous surfaces of theholder 52 to soften so that the outer legs 22 and 23 of each of theconnectors 21 and the member 50 press into the holder to achieve aninterfitting relationship. In so doing, at least a portion of thesurfaces of the channel 53 that touch each of the legs 22 and 23 of eachof the connectors 21 melts slightly to grip the portion of therespective leg pressing against it. The temperature to which a hardgrade of pure vinyl chloride should be heated for this purpose is about300° F to 350° F. The bar 49 is still in place to establish the properspacing between the gripping portions 33 and 34.

The assembly shown in FIG. 4 is then allowed to cool, after which thebar 49 may then be drawn out by means of a hook (not shown) inserted ina hole 54 at the end of the bar. Then the holder 52 may be lifted freeof the block 47 with all of the connectors 21 firmly gripped by theholder. The holder 52 with the connectors 21 firmly embedded in it isthen ready for use, as will be described hereinafter.

One of the disadvantages of using a material such as brass for the block47 is that it has a high coefficient of thermal expansion. As a result,if a large number of connectors 21 is to be held in place by a brassblock to allow a long holder 52, for example a holder approximately 3inches long, to be placed over them, the brass block 47 is likely tocontract so much in cooling that the connectors 21 at the ends of therow will be slightly tilted toward each other and the entire holder 52is likely to acquire a bowed shape. This is not suitable for holding theconnectors 21 for insertion in a printed circuit board. Accordingly, thestructure shown in FIG. 5 may be used in place of the single block 47shown in FIGS. 3 and 4.

The structure in FIG. 5 includes two blocks 56 and 57 which have arelatively high thermal conductivity, such as brass, but which may alsohave a relatively high coefficient of thermal expansion. These blocks 56and 57 are attached to a rod 58 that extends into openings 59 and 61bored into or otherwise formed in the blocks 56 and 57. The rod 58 isrigidly joined to the blocks 56 and 57 by means of set screws 62 and 63.By making the rod 58 of material that has substantially less thermalcoefficient of expansion that the blocks 56 and 57, and by making thepoint of attachment between the rod and the blocks at a middle sectionof the blocks, the thermal expansion of each of the blocks 56 and 57extends away from the point of attachment, i.e. the set screws 62 and63, in the directions indicated by arrows 64-67. In this way arelatively large number of connectors 21, which are here shown cut alongtheir respective center lines, may be mounted so that the relative shiftof position between them is held to a sufficiently low value so that aholder, such as the holder 52 in FIG. 4, having a length of 31/2 inchescan be placed over them without being forced into a curved shape as theblocks 56 and 57 cool.

FIGS. 6-8 show a modified form of holder 69 that has a pair of sidewalls 71 and 72, each of which has a plurality of grooves 73 and 74,respectively, formed in it. Each of these grooves has a depthapproximately equal to the diameter of the wire from which theconnectors 21 are made and a width slightly greater than that diameterto accomodate a slight amount of warping of the connectors out of theirnormal form in which all parts of a connector lie in one plane. Forstrength, the holder 69 has a plurality of transverse walls 76 betweenthe side walls 71 and 72. The holder 69 also has a built-in central bar77 that has a slightly tapered cross-section as shown in FIGS. 7 and 8.

FIG. 8 shows a connector 21 placed in the holder 69 and pressed upwardlyfar enough so that its center 24 is against the upper edge of the bar77. Its outer legs 22 and 23 fit into the grooves 73 and 74,respectively, to be held firmly. The bottom surfaces of the grooves areslanted slightly inwardly to hold the connectors 21 more firmly, and thecentral bar 77 cooperates with grooves to provide accurate alignment ofthe connectors.

FIG. 9 shows the holder 52 with the connectors 21 and the member 50 init aligned over a double row of holes 78 in the printed circuit motherboard 37. The board is also shown as having a second set of holes 79 toreceive a second set of connectors 21. The metallized area around eachhole does not appear on the surface of the board 37 shown in FIG. 9.

FIG. 10 shows the board 37 after the holder 52 has been lowered to allowthe ends of the connectors 21 and the member 50 to extend through theholes 78. A wave 81 of molten solder 82 is shown sweeping the lowersurface of the board 37 in the direction of an arrow 83 to solder eachconnector 21 and the member 52 in place.

FIG. 11 shows the holder 52 moving up in the direction of an arrow 84after having been heated by a source 86, which may be an infra-red lampor a heat gun or another source. The holder could have been removed whenthe connectors 21 and the member 50 were heated by the solder, but to doso might cause a small shift in the location of any connectors embeddedin solder that was still soft. It is better to be sure that the solderhas hardened and then reheat with the source 86.

FIG. 12 shows the completely installed connectors 21 and the member 50about to receive the printed circuit board 36 as it moves in thedirection of the arrow 87. The board 36 has a printed conductive strip88 to be mechanically grasped and electrically connected by each of theconnectors 21. It also has a slot 89 that fits over the upper bar of themember 50 to prevent the board 36 from being installed backward.

While the invention has been described in terms of specific embodimentsand steps, it will be understood that modifications may be made thereinwithin the scope of the following claims.

What is claimed is:
 1. An article of manufacture comprising a pluralityof resilient wire connector members, each formed of an integral piece ofwire bent to comprise a pair of legs extending generally parallel toeach other and an integral, reverse-bent part joining said legs togetherat one end thereof, the other end of each of said legs being free; andaholder for a plurality of said wire members and comprising: a bodyportion comprising a pair of substantially parallel side walls havingsurfaces facing toward each other, each of said walls having parallelgrooves in the facing surface thereof aligned with corresponding ones ofsaid grooves in the facing surface of the other of said walls tocomprise an aligned pair of grooves, said walls being spaced apart by adistance slightly less than the normal distance across said pair of legsto the outermost part of the surfaces of said legs, each of said wiremembers being firmly but releasably held by the inner surfaces of one ofsaid aligned pairs of grooves pressing in opposite directions on saidlegs of the respective wire member, said holder further comprising meansbetween said side walls and parallel thereto to engage the reverse-bentpart of said wire members and provide alignment of the relativepositions of all of said wire members in the direction perpendicular tothe longitudinal direction of said grooves.
 2. The article of claim 1 inwhich said holder is generally U-shaped and encloses all but the freeends of the legs of said wire members.
 3. The article of claim 2 inwhich said holder is a thermoplastic material and each of said groovesis formed in situ in juxtaposed sections of the inwardly-facing wall ofsaid U-shaped holder to conform to the configuration of a contiguousportion of a respective one of said legs.
 4. The article of claim 3 inwhich said wire members are generally M-shaped and said reverse-bentpart comprises a central loop extending in the same direction as thelegs thereof and defined by opposite sides and a bight, each of saidlegs being joined respectively to one side of said loop by additionalcurved sections of said wire, portions of the opposite sides of saidloop closer to their respective juncture with respective legs beingspaced closer together than other portions of the opposite sides of saidloop closer to the bight, said closer-spaced portions defining grippingportions to receive and to grip secondary members of predeterminedthickness, said wall of said holder comprising means to hold each ofsaid wire members with a predetermined spacing between its grippingportions to provide a predetermined gripping pressure therebetween. 5.The article of claim 4 in which at least one of said wire members isgenerally U-shaped and has legs longer than the M-shaped wire members sothat the bight portion of said U-shaped wire member extends more deeplyinto the bight region of said U-shaped holder than do said grippingportions of said M-shaped wire members.
 6. The article of claim 1 inwhich said grooves have bottom surfaces slightly slanted toward eachother to press the free ends of said legs slightly toward each other. 7.The article of claim 1 in which said holder comprises a plurality oftransverse walls extending perpendicularly between said side walls. 8.The article of claim 7 in which said means between said side wallscomprises a central wall parallel to said side walls, said wire membersbeing generally M-shaped and comprising a central loop extending in thesame direction as the legs thereof, each of said legs being joined to arespective side of said loop by additional curved sections of said wire,portions of the sides of said loop being spaced closer together towardtheir respective junctures with the respective legs than toward thebight portion of said loop to define gripping portions to receive and togrip secondary members, said central wall fitting into said central loopto stabilize the positions of said members in said holder.
 9. Thearticle of claim 8 in which each of said grooves has juxtaposedsidewalls spaced apart a distance slightly greater than the diameter ofsaid wire members and a depth substantially equal to the diameter ofsaid wire members.
 10. The article of claim 8 in which said central wallhas a tapered cross-section corresponding generally to the variation indistance between said side of said loop from said gripping portions tosaid bight portion thereof.